Have you tried raising the timing? This seemed to cure some issues a couple of racers over here had when running on E85. Sadly I do not know al the details. But its easy to try, so might be worth a shot?

It may stand a little timing looking at the plugs on gas, but it's close enough it should not be an issue, and would not cause the ET and MPH to be erratic. Run #1 - 8.559/155.252 - 8.611/155.65 Jet up Left Lane poor traction3 - 8.533/155.68 No change back to right lane4 - 8.570/155.27 Went to projected nose plug5 - 8.560/154.77 Back to original plugs, smelled rich so I dropped primary jet only between run 1 & 26 - 8.631/153.58 Dropped float level a little7 - 8.674/153.50 No change, at this point I was worried something else was going on and ended testing.

On the last run the 1/8 mile was a 5.497/124.60. Next day on gas (both carbs are 1150's, changed to old BG regulator) first pass was 5.25/130.

I posted info on floats and N&S in the fuel system section, I new N&S size and pressure would affect the float level, but maybe more than I figured on. I plan to set up a test bowl and measure the effects of pressure and N&S size on float level. I will try to see at a fixed float level at what height a 110 N&S ends up at with 6 PSI, and see what pressure the .140's end up in the same position. I may have just been running too much pressure with a N&S that large, forcing me to drop the N&S/float level down and limiting it's downward travel. It's like it was running out of fuel, just a little erratic. Probably why a belt drive pump with rising pressure works better for Methanol. And may be a good reason for a regulator that has a vacuum port to lower pressure at higher vacuum when using an electric pump.

gdmii did one of those vacuum referenced regulator thingies a few years ago and it did work. He finally found out though that with PCI bowls and dual .150 needle seats he really didn't need more than 8psig fuel pressure. I run a lot less than that with no apparent problems.

Well it was a positive step forward yesterday, although a small one, still positive. If I throw out one run all looks OK, still i think it is a little slower than my gas carb. Here goes.

First run, new regulator .130 primary jet with a PV, .141 secondary.

1.225/3.510/5.467/125.471.233/3.504/5.454/125.85 - made no changes1.228/3.494/5.435/126.63 - jetted to 136 on primary, no secondary change, liked more fuel.1.220/3.458/5.382/127.42 - jetted to 140 primary, since I had nothing bigger for the secondary I did the dreaded...drilled some jets. My .144 drill fit the .141 jet I was using, so I went to a .147 to a .080 jet I will never use. Looked positive...

1.230/3.499/5.442/126.44 - WTF??? Made no changes...

1st round dialed 5.431.225/3.489/5.451/120.43 - on the brakes, would have been about a 5.430 or high 5.42Second round same dial1.228/3.495/5.454/122.78 - brakes again, would have been a mid 5.43Third round same dial1.215/3.477/5.456/117.89 - brakes too much by .0097. Temp had dropped and they had sprayed the track, would have been a 5.41x

Not sure where the 5.38 came from. Relatively consistent/predictable except for that one pass. I think my next mod will be to add more area to the booster insert, see if it is a restriction after the jet. I will add holes in between the slots. And hopefully have the Racepak in for the next race in two weeks, as I am really flying blind on the tune with nothing usable showing on the plugs.

Mark - are you going to get some data with the Racepak before making any more booster mods?

I've been thinking through the booster issue and was comparing the relative opening area of a stock banjo vs. a stock 8 hole annual booster and it looks like the total booster hole area is approx. 40% larger than the banjo passage. Assuming we continue the idea of opening up each of the fuel passages to allow smooth flow (i.e. the jet being the only restriction), I'd think we would want to maintain the +40% relationship after the E85 banjo mods.

Applying this logic to a banjo passage opened to .185 and +40% area needed by the booster holes, it would mean opening up the stock BLP 12 hole billet boosters from .058 to .063. This would make them smaller than the .071 holes in the stock 8 hole boosters, but still provide the +40% ratio. I can't imagine your slots provide less opening area then 12 .063 holes.

I'm an accountant, not a fluid engineer so maybe my logic may be totally off. Part of my (possible flawed) logic was an assumption that the booster openings can be too large and cause a problem and reduce the efficiency of how they pull fuel.

I don't think the slots are an issue either and should be plenty of area, but I will have to see once I get the Vnet cable and get the Racepak installed, hopefully this next week before the race on the 22nd. I also wonder how much there is to gain over racing gas when the combination is well tuned for gas, and also a lot of the guys are running smaller carbs, so if the carb is restrictive on gas for the combo it may show more of a gain on E85 than a larger gas carb. Lots to ponder, it's hurry up and wait to try again.

Booster holes is something I've been considering as well as it looks more and more like I'll have another methanol 1150 before it's over.

Theory, or at least the way I'm thinking is that the size of the holes DOES matter in that air flow by the booster, which is variable according to throttle opening, creates a variable depression in that area and the more air that flows the more that depression will be. The size of the holes in the booster, ie, combined area should have an effect on how much depression is seen in the entire circuit.

I've mentioned this before but the crosswells in my alky Dominator are .206 and the stake tubes are .213. I've never had the banjos out so I don't know what the hole diameter in those are. I've got a set of banjos that I drilled out to .235 and judging from what my alky carb was doing before I modified it I'll need a jet somewhere around .225 to get enough fuel to possibly slow it down from being too rich.

Mark it's a good point you make about the 40% ratio in the booster holes. I'll have to look at that on mine when I finally get some to play with. Right now I'm up to my arse in alimigators with the Dodge tranny and the Camaro engine having a priority at this point in time. I can still think about other stuff though while I'm working on something else. Yup, the old man can still multi-task "some!

The area of or the number of booster fuel outlet holes has no bearing upon the vacuum generated in the well. However it is important to have the fuel outlet area at the booster larger than the delivery tube etc. The whole concept is to have the main jet as the restriction point WITHOUT creating a sequential jetting system. Sequential jetting is when one jet is not sufficiently large enough for the next jet downstream. The first jet (the main jet) cant function with a correct discharge coefficient if there is a restriction downstream. When you only have one single jetting point the discharge coefficient of the jet nearly equals the discharge coefficient of the venturi so your all sweet easily. The problem happens when you exceed 150 ft per second air speed in the venturi. Then the discharge coefficient of the venturi remains a flat line even though the CFM rate is increasing. The liquid control jet doesnt suffer that issue so the system goes rich . Thats why the correct venturi size is important for the expected operation range of the engine.

Thanks Guy's - all good information. I know I won't be out until probably May due to weather (i.e. winter ) and then work commitments in April but my current thought process is to modify the holes as I described and test the carb so that we have another set of comparable data to jmarks results, after all, more info is always better! I can always open them up further if needed, or change to jmarks slot style.

jmarkaudio, Lost a whole post of thoughts, old and slow i guess. I'll try this again, your as delivered blocks #2 taper .160 to .180 bottom to top. another mark uses that taper on 4150 stuff. Mark the .160 ar the bottom, could that be more of a restriction than this well might need on a dominator and especially one as large as yours.On my dominator i use a larger well at the bottom and mine uses a flared booster, which makes it under 1050 ? and it works well on my 415 sb. After saying all that, i,am not saying its right and i would love to improve it even more. That why i love this section on this site and we can all follow and learn together.

Well as far as the mainwell, since my jet is a bit less than the bottom I don't think it is an issue, and gets bigger as it passes the emulsion bleeds to allow expansion. I think a lot of what Mark fixes is the following, too big of a mainwell, transition areas that step down instead of up toward the booster, and booster passage sizing also to make sure there are minimal areas to create turbulence. I would rather keep the mainwell as small as possible so the signal required to lift the fuel is lower, which will also minimize the emulsion needed to lift the fuel. Obviously it can't be so small it becomes a restriction or speeds the fuel up to the point of turbulent flow. Until I can get some O2 info I'm really flying blind. I do have some methanol metering blocks I can try later, but pointless without the data. And they would possibly create a turbulent point at the booster pin.

As far as the flared or skirted booster, that will restrict the airflow and increase the booster signal, if I had an issue at lower speed that might be something to address. Right now my MPH is down over gas, if anything it is an issue getting fuel at the top end. 60 ft times are right there with gas. The good thing is I am not hurting anything and saving a bunch on fuel costs.

I would rather keep the mainwell as small as possible so the signal required to lift the fuel is lower, which will also minimize the emulsion needed to lift the fuel.

Signal is slang for pressure reduction. Pressure is not affected by the size of the well. Pressure reduction in the main well is created by the venturi combination of the main venturi and the booster. The kill bleed air reduces the pressure present in the entire air portion of the main well. Pressure is equal and opposite in all directions in any container and the main well is just a container.

Moving air which is what the kill bleed does to the system has slightly lower pressure that static air because some energy is used to move it so less energy is present as pressure.

Emulsion air1-the top bleeds purpose is to blow fuel towards the booster at a depression that is less than what would be required to lift the fuel without an air jet stream assisting it. Basically its like blowing the froth off your beer and getting it into the engine early. Without this transitional fuel supply there is difficulty in obtaining a nice crossover from transfer slot to mains. 2-The lower bleeds are used to alter the density of the fuel, these bleeds should only flow enough air (the amount is controlled by the MAB) that they form very small bubbles within the liquid filled main well. This situation only exists at low to moderate flow rates. Realize that the vacuum in the main well is not much at low power like 20hp of air flowing down a carby barrel. This is the part where Ethanol differs from Gasoline and Methanol. Gasoline and Methanol change to turbulent flow at very low power levels per barrel approx 30hp for typical racing carbys. Ethanol doesnt. Ethanol stays laminar for much longer as has been already discussed by me here somewhere. That is the big thing to get right. However Ethanol will eventually go to turbulent flow and that point is around 120hp plus per barrel so thats right in the racing zone. That stuffs the tune all up. All of a sudden the fuel flow rate and the vacuum relationship changes. That relationship is called the discharge coefficient. Discharge coefficient is a single number that makes it easy to see the efficiency of the system. The point of transition to turbulent flow is controlled by 2 things --- the DIAMETER of the pipe the liquid is flowing through and the viscosity of the liquid. Surface finish has a small effect. Corners have large effect.

With gasoline and Methanol the turbulent transition point is very low in power and the emulsion system is inside its functioning range during the transition to turbulent flow. With Ethanol that isnt the case. The emulsion is long gone and you just have a single jet carburetor left. With Ethanol to get the emulsion package to work around the transition point you would need a metering block that is taller in height so that the emulsion package can be lower than the kill bleed.

Its the vertical position of the emulsion package that determines the effective range of the package. The emulsion package has to be in the correct vertical position so that air pressure in the air well above the fuel level can force into the main well in small controlled amounts at the right point in time to force the fuel flowing through the main jet to follow the same discharge coefficient as the air flowing through the main venturi. To complicate matters the main well pressure is from the Booster not the main venturi and the engine is fed from the main venturi not the booster. Interesting huh.

While the mainwell does not affect the signal, doesn't it require a stronger signal to lift the fuel, a larger mainwell has more fuel/mass to lift? Reading Carbs and Carburation by Larew, he discusses the difference even when making the emulsion well larger it affects the signal required to start fuel flow. I'll have to dig it out again... And for nothing else, still trying to minimize turbulent points. Or would we be better with a larger mainwell and smaller angle channel, would it create a more turbulent point at the angle channel or would it calm it down? I know, a properly designed and sized venturi, a smooth radius mainwell, spray bar tubes, and a fuel bowl that is not affected by G's would be nice, but we are stuck with making the best out of our Holley carbs for now.

I will juggle the emulsion some once I have the O2's to see how it affects the curve. Having a fuel that flows more laminar should require more emulsion to correct the curve on a booster style carbs, correct? However at the expense of sending it into turbulence sooner... I wonder if one toward the top and one near the bottom might work better, the top helping start the package and bottom curbing it from going too rich up top. Right now I have a kill, .024 in the second and fourth positions in a 5 hole block., the rest plugged. Setting up for emulsion tubes are looking better....

The pressure in the main well is what determines the level of fuel in the well. Once the pressure differential is sufficient to lift the fuel to the outlet it flows. It doesnt matter whether the well is .180" or 2" diameter, the fuel will be lifted to the same height for the same pressure. What happens though is the 2" diameter well takes longer to fill up. That makes it slow to operate so its one way to get flat spots. The Kill bleed interacts with the diameter of the main well to affect the onset of flow or the height of the fuel, your stuck with that effect because the kill bleed is a leak that you have to have to stop siphoning when the engine is turned off.

Changing the diameter of the well alters the effect of the e-bleeds in how they control the viscosity of the fuel in the well. That changes things too. But the height any liquid is lifted to is determined by the pressure difference and the density of the fluid, not the mass of liquid or anything else, its just pressure difference. A manometer reads just the same if its big or small. Galileo established that fact yonks ago and the physics hasn't changed since then. The diameter of the well controls the transition point to turbulent flow. The transition point has to be at the right time so that the air venturi can do its transition to 150 ft per second at the right relationship to the fuel control caused by the viscosity and the ebleeds and the main jet flow coefficient. There is nothing correct at all about a Holley for Ethanol. Read Larew page 19 to 27 ish. He doesnt spell it out like i just did but if you think about it you will see the relationships.

Having a fuel that flows more laminar should require more emulsion to correct the curve on a booster style carbs, correct?

The transition point of ethanol is much closer to the transition point of the air flow through the venturi so emulsion is not as necessary. Read those pages from Larew and have a good hard think about it. Larew's book is about mainly one aspect of carburetor design. He describes how to design a carburetor with virtually no emulsion. That was his world or experience. Thats not what a Holley is. The most perfect carburetor you can make has NO EMULSION. But the design is not suitable for hotrodders. A Holley is a hotrodders carby that has nowhere near good carburetion control. NO fixed venturi booster carby can accommodate perfectly a power range like 2hp to 200 hp per barrel. A perfect carburetor has to be made specifically for the engine it is on and the engine has to be accurately made in repeatable production. Simply something thats not obtained by hotrodders.